This present invention relates to a filter for use in fluid systems, and more particularly, the invention relates to a relief valve for a filter.
Filters are typically constructed from a housing formed of one or more components secured to one another. A filter media, which is typically a pleated type filter media, is disposed within the interior cavity of the housing. The filter media generally has a hollow cylindrical shape, with an exterior surface defining an input side through which dirty fluid enters. The interior surface of the filter media defines a central fluid passage acting as an outlet that receives the cleaned fluid.
Conventional filters include a center tube acting as a filter media support element, which confers to the assembly a certain amount of structural strength, to retain the shape of the central fluid passage which defines the outlet of the filter. In operation, the fluid filter generally receives dirty fluid, for example motor oil, through an inlet of the housing. The fluid passes through inlet faces of the filter media, which can include the outer circumferential surfaces and one or both end side surfaces, and then passes through the filter media where it is filtered. Finally, the fluid exits through the filter media's outlet surfaces, which generally include the inner surfaces, and follows the central fluid passage to a clean fluid outlet of the filter.
One or more valves are typically provided in the fluid filter to control the flow of liquid through the filter. For example, an anti drain back valve may be provided to prevent the liquid from draining from the inlet side of the filter during periods when the liquid pressure is low, such as when the engine or other system using the lubricating system is off. If the lubricating liquid is allowed to drain from the filter, contaminants may re-enter the lubrication system, and upon starting of the engine, there may not be sufficient lubricant available for the mechanical parts.
A relief valve may also be provided in the filter, which permits the lubricant liquid to bypass the filter media under certain conditions. For example, when the lubricant is cold and highly viscous, or when the filter is clogged, it is important to provide an uninterrupted flow of lubricant, even if it is not filtered. The relief valve is generally designed to open under those circumstances, to let unfiltered lubricant pass through a bypass conduit in the filter and to continue to circulate.
Conventional fluid filters, in particular spin-on type oil filters, utilize relief valves that are formed of multiple complex components, some of which are made of metal and others which may be made of plastic materials. The assembly of these valves within the filter may be difficult, as the parts have to be accurately located, and their alignment has to be assured. This results in an expensive procedure that is likely to produce many defective filters, which have to be rejected. These designs add to the production line size, inventory and manpower, increasing the cost and the variance of constructing the filters.
The exemplary embodiments of the present invention provide a non-metallic relief valve, also referred to as a bypass valve, which only has two parts. These parts are designed to be easy to assemble correctly, to reduce the time and cost associated with manufacturing the fluid filter. The reduced parts count also simplifies the manufacturing support necessary for this filter, for example the manufacturing parts inventory.
In one exemplary embodiment, the relief valve includes two parts made of silicone. The exemplary valve opens to the inner diameter of the filter element, such as the central fluid passage, due to the differential pressure across portions of the valve. For example, the valve may be set to open when a pre-set pressure limit or threshold is exceeded, indicating that the lubricant is unable to pass through the filter media in the normal manner.
The valve element may be secured to the filter media via its peripheral edge. For example, a media plug may be mounted on or in the filter media, and may provide a mounting flange or surface on which is disposed the valve element. The valve element and the media plug cooperate to seal the relief passage during normal operation of the filter, when the pressure of the lubricant is below the pre-set pressure threshold. When the threshold is exceeded, the valve element and the media plug cooperate to open the relief passage, and let the lubricant pass through the filter without being filtered.
In one exemplary embodiment, the media plug may have walls that define apertures which connect the inlet portions of the filter with the outlet portions. Under normal operating conditions, the valve element maintains those apertures closed, so that the only passage from the inlet to the outlet portions is through the filter media. However, a threshold value of the pressure in the lubricant fluid can be defined, above which the valve element opens the apertures, and lets the lubricant fluid bypass the filter media. For example, this threshold value may be selected to correspond to clogging of the filter media.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.